The rock-musician-turned-activist Bono wants you to know: You, too, can be a lobbyist, and all you need is an iPhone.

ONE, the anti-poverty group co-founded by Bono, launched an app Wednesday that lets iPhone users call their lawmakers at the touch of a button. It even provides a script of what to say.

The project is one of several efforts by advocacy groups to use mobile technology to harness the power of their grass roots and pressure Members of Congress.

By making it easy for someone to lobby while in line at the post office or while watching television, the group expects to have many more of its 2.5 million grass-roots supporters involved in influencing policy.

"It arms our army with a much more effective and potent organizing tool," Jeff Davidoff, ONE's chief marketing officer, said. "We think that mobile technology is the next step."

Other organizations seem to agree. In the past year, Amnesty International, Human Rights Watch and the American Cancer Society have also created applications for smartphones and portable devices.

Such membership-based nonprofit groups rely on the size of their grass-roots base to influence Congress. Mobile tools make it easier to engage millions of people in those efforts and, as more people use their cellphones to connect to the Internet, to expand their base.

ONE's app, which was developed in partnership with the digital consultancy @radical.media, combines social media tools from Facebook with news about the organization's global work and petitions that call for Congressional action. Users who provide a ZIP code are connected to their Representatives and regional ONE coordinators.

Davidoff said mobile advocacy is designed to enhance, not replace, more traditional ways of influencing lawmakers. ONE still plans to bring hundreds of activists to Capitol Hill each year for in-person meetings.

"We frequently get asked, 'Do we need a large number of people doing small things, or a small number of people doing large things?' The answer is yes to both," he said.

As ONE seeks to expand its base, that means tapping into the technology used by young people.

"We joke that it's about as antiquated to require you to come to ONE.org as it is to be standing on a corner with a clipboard," Davidoff said.

Yet there is no consensus on whether mobile apps can actually change votes on Capitol Hill.

John Murphy, whose Zuri Group creates mobile tools for nonprofits, said the technology's greatest advantage is the ease of sharing information. After signing a petition, ONE app users are prompted to invite friends on Facebook to do the same and to share their action via Twitter.

"Whether it's new dollars or new donors, you do see a bump once you tap into these networks," Murphy said. "Once [users] have taken action, they have the ability to spread the word. That's where we have really seen this gain."

Murphy, who is currently developing a similar application for Save the Children, said his clients seek out mobile tools as a way to stay in touch with individuals who donate — much in the same way they might have used direct-mail campaigns in past decades.

"A key issue for nonprofits is how do you keep people in the loop," he said. "The mobile benefit is that it is keeping supporters close to the organization."

Those individuals can then be called upon to deliver tens of thousands of phone calls or letters to Congress at a moment's notice — and with little effort on their part.

Davidoff said ONE expects to have more than 100,000 users for its app by next year. The global group plans to make it available for non-iPhone users and to customize it for lobbying foreign governments.

Digital lobbying may streamline the process, but some question its efficacy.

Christopher Kush, CEO of Soapbox Consulting, trains activists on how to lobby Congress. In 2000, he published a book called "Cybercitizen" that predicted the Internet would lead to a "re-launch of American democracy."

A decade later, he is not so sure.

"Really participating in the battle over issues takes a long-term commitment. ... Somebody whose expectations are instant, could you count on that person to stick with the issue? I don't know," he said.

Kush, who has organized in-person advocacy events for ONE, said substantive lobbying by a few hundred dedicated activists is more effective than electronic form letters sent by thousands. Mobile tools may help groups engage activists, but their growing popularity risks adding to — rather than cutting through — the noise.

"Anyone who would suggest that in a busy, tech-savvy world, that Americans now simply need to click on their phones and the United States Congress will be processing that, I think that's an overstatement of how this stuff could be useful," he said.

Part of the problem is that, while other industries have adopted new technologies, government and its influencers are still conducting business in old-fashioned ways, state lobbyist Shawn Miller said.

The Oregon resident developed a mobile app, VoteCount, to do away with the pen-and-paper counting methods lobbyists use to track votes.

"We have to be behind the curve if we're still using paper," he said.

Still, he agreed with Kush that technology cannot replace the value of relationships with lobbyists and advocates trying to influence policy.

"I don't see [apps] changing the more personal aspect," Miller said. "That's pretty central to what we do."